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巨桉(Eucalyptus grandis)是一种优良的速生用材树种,了解氮(N)和磷(P)对巨桉生长、养分限制、化学计量特征的影响对于科学合理施肥具有重要意义。该实验以巨桉无性系组培苗为研究对象,通过在酸性紫色土中设置不同施N或施P梯度,研究巨桉幼苗各器官(根、茎、叶)生物量及碳(C)、N、P的分配和化学计量特征以及巨桉生长的养分限制状况。结果表明:施N处理对巨桉根茎叶及总生物量的影响极显著,增加了地上部分的生物量比例而显著降低了根系的生物量比例;施P对巨桉幼苗总生物量影响不显著,但显著提高了根的生物量分配比例,对茎和叶的生物量分配没有显著影响。施N或施P显著改变了巨桉幼苗的N、P含量和化学计量比,同时也显著影响了土壤与植物N:P的关系。施N可以促使酸性紫色土条件下巨桉对N的吸收而抑制对P的吸收,施P则促进巨桉幼苗对P的吸收。施N对巨桉幼苗根茎叶的C、N、P分配特征有极显著影响,而施P对巨桉幼苗根茎叶的C、N、P分配没有显著影响。施N极显著降低了巨桉幼苗N的利用率,显著提高了P的利用率,而施P处理极显著降低了巨桉幼苗P的利用率。从巨桉生物量沿施肥梯度和N:P的变化规律可以判断,当叶片N:P<15时,巨桉的生长主要受到N的限制作用。施N可以显著地提高根茎叶的N:P比值,缓解巨桉缺N的现象,施P则进一步加剧了N元素的缺乏。
Eucalyptus grandis is an excellent species of fast-growing timber. Understanding the effects of nitrogen (N) and phosphorus (P) on the growth, nutrient restriction and stoichiometry of Eucalyptus grandis is of great importance for scientific and rational fertilization. In this experiment, the clones of Eucalyptus grandis clones were used as research objects. The biomass and carbon (C) of organs of Eucalyptus grandis seedlings (roots, stems and leaves) were studied by setting different N or P gradients in acidic purple soil. N, P distribution and stoichiometric characteristics as well as the nutrient limitation of Eucalyptus grandis. The results showed that the effects of N treatment on Eucalyptus grandis root, stem, leaf and total biomass were extremely significant, which increased the proportion of above-ground biomass and significantly reduced the proportion of biomass in root system. However, application of P had no significant effect on the total biomass of Eucalyptus grandis seedlings , But significantly increased the proportion of biomass allocated to the roots and had no significant effect on the biomass allocation to the stems and leaves. Application of N or P application significantly changed the N, P and stoichiometry of E. grandis seedlings, but also significantly affected the relationship between soil and plant N: P. Application of N could promote the absorption of N under Eucalyptus urophylla under acid purple soil conditions and inhibit the absorption of P, while P promoted the absorption of P by E. grandis seedlings. N application had a very significant effect on the distribution of C, N and P in roots, stems and leaves of E. grandis seedlings. However, application of P had no significant effect on the distribution of C, N and P in roots and leaves of E. grandis seedlings. N application significantly reduced the N utilization rate of E. grandis seedlings and significantly increased the utilization rate of P, while P treatment significantly reduced P utilization rate of E. grandis seedlings. According to the fertilization gradient and N: P variation of E. grandis biomass, the growth of E. grandis was limited by N when leaf N: P <15. N application can significantly improve the N: P ratio of roots and leaves, ease Eucalyptus lack of N phenomenon, P is to further aggravate the lack of N elements.